The present invention relates to a method of producing front axles for industrial vehicles.
At present, in the development of road vehicles, particularly industrial vehicles, increasing attention is being given to reducing the environmental impact and fuel saving which can be achieved by way of reduced consumption. From this point of view, one of the principal objects of the road vehicle industry is to improve the performance/weight ratio of vehicles.
A decrease in the weight of vehicles could be obtained by using lighter materials for some components of the vehicle, for example magnesium or aluminum alloys instead of conventional steels. However, this approach is not possible for certain applications in which the component is subject to heavy mechanical loading, for example in the case of axles.
At present, front axles comprise solid-section beams produced by a forging or casting process. Although axles of this type have satisfactory mechanical characteristics, they are, nevertheless, of particularly high weight and, for the above-mentioned reasons, they contribute in a not insignificant manner to the total weight of the vehicle and, therefore, to consumption and emissions.
The above-mentioned drawback could be obviated by using special non-ferrous alloys (for example, titanium) which are lighter and have high mechanical strength; however, such materials are very expensive.
Attempts have been made to produce hollow-section front axles by using non-conventional manufacturing processes such us hydroforming; however, these processes are very difficult to control and have substantial limitations as to the shape of the hollow body to be produced; in particular, known hydroforming processes can be used to obtain substantially straight tubular shapes, but cannot be used to produce shaped front axles having inclined or bent end portions, as is normally necessary in order to allow the axle to be housed below the engine of the vehicle. Therefore, to the applicant""s knowledge, hydroformed axles have never been industrially successful.
The object of the present invention is to devise a method of producing front axles for industrial vehicles, which makes it possible to solve the problems of the prior art, and which allows, in particular, to produce shaped hollow front axles in a simple and economical manner.
This object is achieved by the present invention in that it relates to a method of producing front axles for industrial vehicles, characterized by comprising the steps of:
providing a tubular blank;
forming end portions of said tubular blank so as to obtain a first axis-symmetrical intermediate product having a central portion with the same diameter as said blank, reduced-diameter ends and tapered portions connecting said central portion to said ends;
crushing said first intermediate product so as to obtain a second intermediate product having a central portion with an elongated cross section and intermediate portions connecting said central portion to said ends and having a cross section evolving from elongated to substantially round; and
finishing said axle by means of at least one forming step carried out by hydroforming.